Carbon for arc lights



Jan. 2 2, 1946. Q 2,393,396

CARBON FOR ARC LIGHTS Filed Jan. 25, 1945 INVENTQR Ernest M Miller:

v ATTORNE-Y Patented Jan. 22 1946 CARBON FOR ARC LIGHTS Ernest Mason Miller, North Hollywood, Calif.,

assignor to Twentieth Century-Fox Film Corporation, Los Angeles, Calif., a corporation of New York Application January 25, 1943, Serial No. 473,488

. 2 Claims.

This invention relates to electric arc lights and deals particularly with carbons used in lights of this nature.

The invention to be hereinafter described has been developed for a special use in motion picture studios but to those versed in the art it will become evident that it may be used to good advantage in other fields wherever a high intensity carbon are light is required. V

' In using carbons in arc lights, particularly for motion picture work, a highly objectionable feature is the sputtering of the light between the carbons. This may be caused by'a variety of things but is probably mainly due to escaping gas from the crater of the carbon. As is customary, carbons, and especially the carbon used on the positiveside of the arc, are made with a comparatively hard, brittle shell surrounding a soft core. The core is generally made of a granular substance held together by a suitable binder. In the intense heat generated by the arc, gas is liberated from this core, which because of the outer impervious shell must escape through the crater in the are. This causes sputtering of the are, which has two very bad eifects. One is to fluctuate the light value, which cannot be tolerated in motion picture work, and the other is to pit reflecting mirrors which are positioned close to the arc by the hot particles thrown oif from the crater. To overcome these objectionable features, I conceived of a way whereby the gas and molten material generated by the heat could escape some other way than through the crater itself. The method is simpleand efiicient and requires only that the shell itself be porous or that a series of small holes be drilled through the shell so that the -gas and molten material resulting from the fusing of the core can escape through the holes which heretofore could be used only up to a certain definite amperage without the holes could be used with adefinitely higher amperage after the holes had been drilled and accordingly could be made to yield a marked increase in the amount of light produced.

An object of my invention, therefore, is to provide a means for improving the conventional carbons for are lights so that they may be used with I a higher amperage to yield a greater light value.

Another object is to provide a carbon having a shell surrounding a core with the outer shell so formed that gas and/or molten material may escape from the inner core through the outer shell. r

Other objects and advantages will become apparent as the description proceeds in conjunction cient to state that-the holes should be of suflicient diameter and sufliciently close to each other to permit molten material and gases to flow backward from the crater and escape through the holes. As shown and as previously mentioned,

the carbon comprises a shell l3 surrounding a core 14 and as seen on the end of the carbon the holes l2 penetrate through the shell I3 and form a passageway from the core through the shell. 7 After it is drilled, the carbon is used in the conventional manner and is mounted-in the holders in the usual way. In practice it has been found that satisfactory results are obtained if the positive carbon only is treated in the manner stated.

'As the carbon is fed into the arc, a crater is formed and the carbon is eaten away, but there is always a hole l2 near the crater to permit escape of the gas and molten materiaL- This has been found to eliminate all sputtering and has allowed increased amperages to be used on standard carbons high above their manufactured rating, with the result that a higher light intensity may be obtained from a conventional carbon.- Amperages have been increased almost 100% over the conventional rating with satisfactory per- 7 formance on standard carbons that have been drilled with holes according to my invention.

-It is to be understood that'the size and number of holes drilled in the carbon may be varied to suit requirements, which if carried to a logical conclusion would result in a carbon having a porous shell. The invention is accordingly intended to cover this form and all other modifications and refinements in construction and ar- 2. For use in an are light a. carbon consisting 1 of a substantially solid non-metallic body having an inner core of flame producing material, said body forming a reiatively hard outer shell sur-' rounding and contacting said core at all places with holes extending radially through said shell to said core to permit products of combustion to escape therethrough.

ERNEST Mission-"MILLER. 

